Retaining walls are used in landscaping around residential or commercial buildings. Retaining walls can be made of various materials, but for reasons of durability are most often either concrete structures cast in situ or walls formed of stacked courses of natural stone or masonry blocks. Concrete masonry blocks have become the most popular retaining wall components, due to their ease of manufacture, transport and handling. The blocks are stacked either manually or with the aid of machinery.
Conventional concrete masonry blocks are either wet cast or dry cast. In the dry cast process, a concrete mixture is filled into a mold box and compressed to generate a pre-consolidated block. This pre-block is removed from the mold box and transported to a setting location at which the block is stored for setting of the concrete mixture. Several methods have been developed to provide hollow dry cast blocks with a textured front surface. Molding a slab including several blocks and subsequently braking the slab into individual blocks allows for the creation of an irregular, rough front surface similar to the surface of a split natural stone. Such blocks are generally referred to as split face or hardsplit blocks. Alternatively, the smooth front surface of a finished molded block can be subjected to a percussive treatment, which brakes up and roughens the front surface. Finally, a three dimensional surface structure can be embossed into the front surface of the block during compression of the concrete mixture in the mold.
A retaining wall is also known from WO2008092237, which system includes base or wall blocks forming the actual retaining wall and decorative facing blocks or panels, which are mounted onto the wall blocks to form a decorative facing on the retaining wall. In that system, the wall blocks are of sufficient size and mass to perform the retaining function. They may even be able to support the facing blocks or panels. Although that system is very flexible, since the retaining wall can be provided with many different facing surfaces, which can even be exchanged without dismantling the wall, the base blocks suffer from the same drawbacks as other known retaining wall blocks.
The performance of retaining walls or freestanding walls is generally determined by the height of the wall, the overall mass of the wall and the width or thickness of the wall at the base, with the mass being the most critical. Local building code requirements dictate the forces such walls must be able to withstand, which in turn limit the design possibilities in terms of maximum wall heights for a given width and mass of a wall. Generally, the larger the mass and the width of the wall at the base, the base width, the higher the retaining capacity or resistance to tipping of the wall. More generally, the higher the mass, the higher the retaining capacity of the wall. This must be taken into consideration when building retaining walls of stacked blocks. In a conventional retaining wall of monolithic, stacked blocks, the wall blocks themselves must have a sufficient width to provide the minimum base width and mass required for the retaining wall. This in turn limits the maximum length and height of retaining wall blocks useful for manual installation. It also limits the overall retaining capacity achievable with conventional, manually installed, stacked block walls. As a result, retaining walls of higher retaining capacity are either cast in situ or made of large blocks which must be handled with often specialized machinery. The exposed length and height of an installed retaining wall block are normally referred to as the length and height of the block, while the remaining dimension of the block is referred to as the width of the block. To address the problem of excessive weight of conventional retaining wall blocks, hollow retaining wall blocks have been developed in an effort to reduce block weight and to thereby expand the size range of manually installed blocks. However, using hollow blocks reduces the overall mass of the stacked retaining wall and, thus, limits the retaining capacity of the wall achievable with hollow blocks. Thus, the height and retaining capacity of retaining walls made of conventional monolithic blocks for manual installation is limited, even if the blocks are sized for maximum retaining performance (optimum width) and maximum coverage (maximum length and/or height).
Conventional retaining wall blocks are often tapered towards the back to allow a curved placement of the blocks for the assembly of curved walls. In walls with convex curvature, the blocks then touch at the tapered sides, while in a straight line installation or in walls of concave curvature the blocks only touch at their front edges and comparatively large triangular gaps or spaces are defined between the blocks at the back. Those gaps are disadvantageous, since they reduce the overall mass of the wall and therefore the retaining capacity of the wall.
Modular retaining wall systems made of interconnected facing blocks and buried, spaced apart backer blocks are known from U.S. Pat. No. 4,068,482, U.S. Pat. No. 5,350,256, U.S. Pat. No. 5,468,098, U.S. Pat. No. 5,688,078, U.S. Pat. No. 7,503,729 and US200910041552. In those conventional walls, the wall of stacked facing blocks principally function as the principle material retaining component of the retaining wall, while the backer blocks have an anchoring function to reduce the tendency for tipping of the wall. The backer blocks are generally spaced apart and buried within the material to be retained and, thus, do not contribute to the mass and width of the wall.
Retaining wall systems including stacked blocks with interlocking projections for forming a hollow wall with front and back partial walls and intermediate connectors are disclosed in U.S. Pat. No. 4,490,075, U.S. Pat. No. 5,403,127 and DE 2549162. However, the connectors in those systems interlock with the blocks in the front partial wall in such a way that the ends of the connectors/spacers between the front and back partial walls are visible in the installed condition, giving the wall an artificial rather than natural appearance.
Thus, a modular retaining wall system which overcomes at least one of these disadvantages is desired.